1. Field of the Invention
The present invention relates to a drive unit of a display panel for active driving light-emitting elements constituting pixels, and more particularly, to a drive unit and a drive method of a light-emitting display panel for realizing low power consumption by selecting a partial display mode for controlling light emission making use of a part of the effective light-emitting elements disposed in a display panel.
2. Description of the Related Art
Displays using a display panel composed of light-emitting elements disposed in a matrix shape are under extensive development. Attention is given to organic electroluminescence (EL) elements using, for example, an organic material in the light emitting layers thereof as the light-emitting elements used in the display panel. This is because the efficiency and life of the organic display panel have been improved to a practically usable level by using an organic compound promising good light emitting characteristics in the light-emitting layers of the EL elements.
There have been proposed, as the display panel using the organic EL elements, a simple matrix type display panel in which EL elements are simply disposed in a matrix shape and an active matrix type display panel in which drive elements composed of, for example, TFTs (Thin Film Transistors) are added to the respective EL elements disposed in the matrix shape. The latter active matrix type display panel is suitable for a high-definition display because the latter display panel has such characteristics that it can realize lower power consumption than the former simple matrix type display panel and that it has a less amount of crosstalk between pixels.
In particular, nowadays, the application of the self-emitting type displays described above to hand-held type terminal equipment, and the like, which are typically represented by portable phones, has been partly realized, and the equipment more and more requires low power consumption. To realize the low power consumption, it is effective, in an example of, for example, the portable phones, to select a partial display mode for controlling light emission making use of only a part of the effective light-emitting elements of a display in a waiting mode.
Incidentally, in the active matrix type display panel described above, a data driver and a scan driver are designed so as to be arranged on, for example, a glass substrate, on which a display pixel section is formed, so that the number of signal lines connected between the display panel and external circuits is reduced as much as possible. When it is intended to realize the partial display described above in the above circumstances, it is necessary to add a partial drive circuit to the scan driver.
FIG. 1 schematically shows an example of a display screen, in which a display region is formed, for example, between a scan start position (START) and a scan end position (END), when the partial display is executed. When the partial display is executed, it is necessary to input a start signal at the START position and to clear a shift register in the scan driver at the END position.
To permit a scan to be started from an arbitrary line on an effective display screen as shown in FIG. 1, a register for setting a scan start position, a decoder for enabling the value of the register to respective scan lines, and the like are necessary. When it is assumed that the total number of the scan lines is, for example, 240, a decoder for making conversion from 8 bits to 240 bits is necessary, and the scale of the decoder is made very large. Further, gates and the wirings thereof are necessary to reset the shift resister.
When the wirings described above are added to the active matrix type display panel, it is anticipated that the number of TFTs constituting the scan driver will be at least quadrupled. According to this arrangement, it is contemplated that the ratio of the glass substrate occupied by the scan driver increases from, for example, 5% to 20%. As a result, an active area is forced to be reduced by about 15% and thus an opening ratio is reduced, which requires to increase the instant luminance of light-emitting elements in order to obtain predetermined luminance.
Accordingly, when it is intended to realize the partial drive in the conventional active matrix type display panel, there is a technical problem in that low power consumption cannot be realized as a whole due to an increase in the electric power consumed by the circuits added as described above and to an increase in the electric power consumed to increase the instant luminance of the EL elements.
An object of the present invention, which was made based on the technical point of view described above, is to provide a drive unit and a drive method of a light-emitting display panel capable of realizing a partial drive without the addition of a complex control circuit added thereto and reducing power consumption thereby in an active matrix type display panel in which a data driver and a scan driver are arranged on the same substrate constituting the display panel.
In a drive unit of an active matrix type display panel according to a first embodiment of the present invention, which was made to solve the problems described above, having a plurality of light-emitting elements which are disposed at the intersecting positions where a plurality of data electrode lines and a plurality of scan electrode lines intersect and the light emission of which is controlled by drive circuits, respectively, the drive unit is characterized by including a data driver for supplying image data to the respective data electrode lines, a scan driver for sequentially supplying a scan signal to the respective scan electrode lines, and control means for stopping the operation of the data driver when a partial display drive for controlling the light emission of a part of the effective light-emitting elements in the display panel is executed and when the scan driver scans a non-display region.
In this case, it is preferable that the data driver and the scan driver be disposed on the same substrate constituting the display panel together with the respective drive circuits and the respective light-emitting elements corresponding thereto. Further, the drive circuits are preferably composed of control transistors for transmitting image data supplied from the data driver based on a scan signal supplied from the scan driver and drive transistors for supplying a drive current to the light-emitting elements based on the image data transmitted by the control transistors.
Then, in a preferable embodiment, the data driver may include a shift register for capturing serial image data as parallel image data by sequentially shifting up the serial image data based on a clock signal and a latch circuit for outputting pixel unit image data to the respective data electrode lines by latching the image data captured by the shift resister based on a latch signal. Further, the scan driver may include a shift register for outputting a scan signal to the respective scan electrode lines by sequentially shifting up it based on a clock signal.
Then, it is preferable that the drive unit include a black data set means for capturing black data for controlling the light-emitting elements in a non-lighting state for at least one horizontal period when a scan is executed from a display region to a non-display region while the partial display drive is being executed to control the light emission of a part of the effective light-emitting elements in the display panel.
In contrast, in a drive method of the active matrix type display panel according to the first embodiment of the present invention having a plurality of light-emitting elements which are disposed at the intersecting positions where a plurality of data electrode lines and a plurality of scan electrode lines intersect and the light emission of which is controlled by drive circuits, respectively, a data driver for supplying image data to the respective data electrode lines, and a scan driver for sequentially supplying a scan signal to the respective scan electrode lines, the drive method executes a black data set step of capturing black data for controlling the light-emitting elements in a non-lighting state for at least one horizontal period when a scan is executed from a display region to a non-display region while a partial display drive is being executed to control the light emission of a part of the effective light-emitting elements in the display panel, and a step of scanning the non-display region with the scan signal from the scan driver in a black data set state that is set by the data driver.
In this case, it is preferable that the supply of a clock signal for driving the data driver be stopped while the step of scanning the non-display region is being executed.
According to the drive unit of the first embodiment of the present invention employing the drive method described above, when an ordinary display drive or a partial display expressed as a partial display drive is executed, the scan driver continues a state in which one frame (or one sub-frame) is sequentially scanned at all times based on a scan start signal. Then, when the non-display region is scanned by executing the partial display, the drive of the data driver is stopped. This is executed by, for example, stopping the clock signal supplied to the data driver.
As described above, since the data driver that operates at a high speed is temporarily stopped when the non-display region is scanned, low power consumption can be realized. Thus, when the width of the display region is small with respect to a scan direction, low power consumption characteristics can be obtained accordingly.
In contrast, in a drive unit of an active matrix type light-emitting display panel according to a second embodiment of the present invention having a plurality of light-emitting elements which are disposed at the intersecting positions where a plurality of data electrode lines, a plurality of scan electrode lines, and a plurality of erase electrode lines intersect and the light emission of which is controlled by drive circuits, respectively, the drive unit is characterized by including a data driver for supplying image data to the respective data electrode lines, a first scan driver for sequentially supplying a scan signal to the respective scan electrode lines, a second scan driver for supplying an erase signal to the erase electrode lines, and control means for stopping the operation of the data driver when a partial display drive for controlling the light emission of a part of the effective light-emitting elements in the display panel is executed and when the first scan driver scans a non-display region as well as for forcibly extinguishing the light-emitting elements corresponding to the non-display region by supplying an erase signal to the erase electrode lines corresponding to the non-display region from the second scan driver.
In this case, it is preferable that the data driver, the first scan river, and the second scan driver be disposed on the same substrate constituting the display panel together with the respective drive circuits and the respective light-emitting elements corresponding thereto. Further, the drive circuits are preferably composed of control transistors for transmitting image data supplied from the data driver based on the scan signal supplied from the first scan driver, drive transistors for supplying a drive current to the light-emitting elements based on the image data transmitted by the control transistors, and erase transistors for disabling the operation of the drive transistors based on the erase signal supplied from the second scan driver.
In a preferable embodiment, the second scan driver may include a shift resister to which erase control data corresponding to a partial display pattern is set based on a clock signal. Then, it is preferable that the erase control data corresponding to the partial display pattern be set to the shift resister in the second scan driver during a preparation frame period.
In addition, it is preferable that black data for controlling the light-emitting elements in a non-lighting state be captured by the shift resister in the data driver during the preparation frame period. Further, it is preferable that the first scan driver be arranged to stop its operation during a period until the starting point of a next one frame or one sub-frame is scanned after the first scan driver has scanned the final display region of one frame or one sub-frame.
In any arrangement of the first and second embodiments described above, it is preferable that the light-emitting elements be composed of organic EL elements using an organic compound in the light emitting layers thereof.
In contrast, in a drive method of an active matrix type display panel according to the second embodiment of the present invention having a plurality of light-emitting elements which are disposed at the intersecting positions where a plurality of data electrode lines, a plurality of scan electrode lines, and a plurality of erase electrode lines intersect and the light emission of which is controlled by drive circuits, respectively, a data driver for supplying image data to the respective data electrode lines, a first scan driver for supplying a scan signal to the respective scan electrode lines, and a second scan driver for supplying an erase signal based on a partial display pattern to the respective erase electrode lines, the drive method executes a step of setting the erase data based on the partial display pattern to the second scan driver, a step of executing a partial display based on the image data supplied from the data driver when a display region is scanned with the scan signal from the first scan driver, and a step of forcibly extinguishing the light-emitting elements corresponding to a non-display region based on the erase data set to the second scan driver when a scan is executed from the display region to the non-display region.
In this case, it is preferable that the drive of the data driver be stopped as well as that the first scan driver stop its operation during a period until the starting point of a next one frame or one sub-frame is scanned after the first scan driver has scanned the final display region of one frame or one sub-frame in the state in which the non-scan region is scanned. In addition, it is preferable that a step of capturing black data for controlling the light-emitting elements in a non-lighting state by the shift resister in the data driver be executed just before a step of setting the erase data based on the partial display pattern to the second scan driver is executed.
According to the drive unit of the second embodiment of the present invention employing the drive method described above, when the partial display expressed as the partial display drive is executed and the non-display region is scanned, the drive of the data driver is stopped similarly to the drive unit of the first embodiment described above. This is executed by, for example, stopping the clock signal supplied to the data driver. Thus, low power consumption can be realized because the data driver operating at a high speed is temporarily stopped.
Further, according to the drive unit of the second embodiment of the present invention, the first scan driver can stop its operation during a period until the starting point of a next one frame or one sub-frame is scanned after the first scan driver has scanned the final display region of one frame or one sub-frame. This is because the erase data based on the partial display pattern is preset to the second scan driver and the light-emitting elements corresponding to the non-display portion are forcibly extinguished thereby. Thus, according to the drive unit of the second embodiment, lower power consumption can be realized because the first scan driver can be also stopped in a non-display period of time.